/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.solr.search;

import org.apache.lucene.search.Query;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import java.util.List;

/**
 * A hash key encapsulating a query, a list of filters, and a sort
 * 
 */
public final class QueryResultKey {
	final Query query;
	final Sort sort;
	final SortField[] sfields;
	final List<Query> filters;
	final int nc_flags; // non-comparable flags... ignored by hashCode and
						// equals

	private final int hc; // cached hashCode

	private static SortField[] defaultSort = new SortField[0];

	public QueryResultKey(Query query, List<Query> filters, Sort sort,
			int nc_flags) {
		this.query = query;
		this.sort = sort;
		this.filters = filters;
		this.nc_flags = nc_flags;

		int h = query.hashCode();

		if (filters != null) {
			for (Query filt : filters)
				h += filters.hashCode();
		}

		sfields = (this.sort != null) ? this.sort.getSort() : defaultSort;
		for (SortField sf : sfields) {
			h = h * 29 + sf.hashCode();
		}

		hc = h;
	}

	@Override
	public int hashCode() {
		return hc;
	}

	@Override
	public boolean equals(Object o) {
		if (o == this)
			return true;
		if (!(o instanceof QueryResultKey))
			return false;
		QueryResultKey other = (QueryResultKey) o;

		// fast check of the whole hash code... most hash tables will only use
		// some of the bits, so if this is a hash collision, it's still likely
		// that the full cached hash code will be different.
		if (this.hc != other.hc)
			return false;

		// check for the thing most likely to be different (and the fastest
		// things)
		// first.
		if (this.sfields.length != other.sfields.length)
			return false;
		if (!this.query.equals(other.query))
			return false;
		if (!isEqual(this.filters, other.filters))
			return false;

		for (int i = 0; i < sfields.length; i++) {
			SortField sf1 = this.sfields[i];
			SortField sf2 = other.sfields[i];
			if (!sf1.equals(sf2))
				return false;
		}

		return true;
	}

	private static boolean isEqual(Object o1, Object o2) {
		if (o1 == o2)
			return true; // takes care of identity and null cases
		if (o1 == null || o2 == null)
			return false;
		return o1.equals(o2);
	}
}
